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Simon Benjamin

Professor Simon Benjamin
Professor of Quantum Technologies

Department of Materials
University of Oxford
16 Parks Road
Oxford OX1 3PH
UK

Tel: +44 1865 273732 (Room 195.40.02)
Tel: +44 1865 273777 (reception)
Fax: +44 1865 273789 (general fax)

QuNaT Group

Summary of Interests

1. New technologies that explaoit quantum physics: quantum sensors, quantum communications, and quantum computing. Theory to support the developement of these technologies on various platforms, including novel silicon and diamond based materials. 

2. Energy harvesting, transfer and storage understood at the quantum level. Modelling of energy flow phenomena in both artificial and living (e.g. photosynthetic) systems. 

Current Research Projects

Coherent Control of Spin Systems
Dr. S.C. Benjamin, Dr. B.W. Lovett*, Dr. E.M. Gauger
We are studying the quantum properties of nuclear and electron spins, primarily in molecular systems. Our aim is to provide theory that will allow for the control small numbers of spins, such that the quantum coherence is preserved for as long as possible. We collaborate with the Quantum Spin Dynamics experimental group in London (http://www.ucl.ac.uk/qsd), and together we demonstrated that the quantum state of an electron spin can be transferred coherently to a nuclear spin, thus increasing the coherence time. We are now working on optical methods for further improving coherence, and for coupling several spins together. (*Heriot-Watt University)

Architectures and materials for robust and scalable quantum technologies
Dr. S.C. Benjamin, Ms Naomi Nickerson
Today's computers may seem very powerful, but their designs do not take advantange of the enormous potential power of quantum physics. We know that it is possible, in principle, to build an entirely new class of technology that would harness effects like quantum superposition and quantum entanglement in order to profoundly outperform all conventional machines (at least for certain key tasks). However such technologies are very challenging to build in reality. It particular it is difficult to take the small prototype systems in the laboratory and scale them up to the point that they start to exceed the capacities of conventional technologies.  This project is about finding ways to build these technologies that are robust, in the sense that they can operate with realisitic levels of imperfection, and also scalable -- so that once you have a few components working together, it is straightforward to add more and more. For example: One approach would be to build the large machine by networking together many simple processor cells, thus avoiding the need to create a single complex structure. See for example our open Nature Communications paper: http://www.nature.com/ncomms/journal/v4/n4/full/ncomms2773.html

Quantum energy calculations for artificial and biological nanostructures
Dr. S.C. Benjamin, Dr. B.W. Lovett*, Dr. E.M. Gauger, Mr Higgins, Mr Pollock
In order to best understand how to engineer molecular scale systems that can harvest, transfer and store energy, it is necessary to understand energy transfer at the quantum level. There is evidence to suggest that Nature's molecular technologies, for example the structures involved in photosynthesis, perform energy transfer in a way that involves quantum coherence. This is a surprise since quantum effects are usually thought to be difficult to achieve and more the province of the physics laboratory than a "warm and wet" biological system. We are developing new analytic and numerical techniques to understand energy transfer as a fully quantum mechanical process, and aiming to apply this both to natural systems and to artificial structures created by our experimental collaborators. The task is challenging, but the answers may eventually allow us to design highly efficient molecular scale technologies.(*Heriot-Watt University)

Quantum superposition in large systems
Dr. S.C. Benjamin, E. Gauger, Professor G.A.D. Briggs, G. Knee
This is a theoretical project looking at the possibilities inherent in creating quantum superpositions of large objects such as massive molecules or SQUIDs and similar. A key theoretical tool is be the Leggett-Garg inequality, which tests to see if a system needs quantum physics to describe its behavoir. We are now buildings on the early success of this project, which we reported in this open Nature Communications paper: http://www.nature.com/ncomms/journal/v3/n1/full/ncomms1614.html

4 public active projects

Research Publications

Nickerson, N., Li, Y. and Benjamin, S. C., 'Topological quantum computing with a very noisy network and local error rates approaching one percent' Nature Communications 4, Article 1756 (2013) OPEN article http://www.nature.com/ncomms/journal/v4/n4/full/ncomms2773.html

Li, Y., Barrett, S., Stace, T. and Benjamin, S. 'Long range failure-tolerant entanglement distribution' New J. Phys. 15 023012 (2013)

Knee, G. C., Briggs, G. A. D., Benjamin, S. C. and Gauger, E. M., 'Quantum sensors based on weak-value amplification cannot overcome decoherence, Phys. Rev. A 87, 012115 (2013)

Ping, Y., Lovett, B. W., Benjamin, S. C. and Gauger, E. M., Practicality of spin chain 'wiring' in diamond quantum technologies, Phys. Rev. Lett. 110, 100503 (2013)

Ping, Y., Gauger, E. M., and Benjamin, S. C. 'Measurement-based quantum computing with a spin ensemble coupled to a stripline cavity' New J. Phys. 14, 013030 (2012)

Knee, G. et al, 'Violation of a Leggett–Garg inequality with ideal non-invasive measurements' Nature Communications 3, Article number: 606 (2012) OPEN article http://www.nature.com/ncomms/journal/v3/n1/full/ncomms1614.html

Projects Available

Imperfect quantum technology: Exploiting first generation quantum computers
Prof S C Benjamin

Simon Benjamin has an ongoing theory project which uses conventional supercomputers to predict the behaviour of 1st generation quantum computers including their limitations and flaws.

Background: Many research groups around the world are getting close to realizing the first generation of a profoundly powerful new class of technology: quantum computers. Building such a machine means learning to control qubits (quantum bits). Different approaches are being tried: qubits may be individual atoms, or nanostructures in diamond, or superconducting loops. But all have one thing in common: the control we can achieve is far lower than the control we have over bits in conventional computers. The first generation of quantum computers will therefore be imperfect, by comparison to our reliable conventional technologies, but they will still have the potential to be vastly more powerful. 

The project: Since 1st generation quantum computers will have imperfect qubits, therefore one must look for tasks that can be successfully performed even in the presence of small errors. A priority would be to study certain physical systems that Oxford experimentalists are working on, especially a hybrid matter-light networks, but the approach would also apply to pure optical processors, monolithic matter systems include superconducting systems, and some alternative approaches such as the D-Wave systems. We also use conventional supercomputers, including the Oxford-based dedicated NQIT cluster operated by ARC which has a value of ~£700,000 to predict which of the many tasks that are suggested for quantum computers can in fact operate successfully in the presence of errors.

This project would suit a student with a strong physics background who wants to work on a theory topic – someone who is interested in analytic “pen and paper” theoretical analysis as well as programming for numerical simulations on high powered computers. 

This NQIT hub EPSRC-funded 3.5-year DPhil in Materials studentship will provide full fees and maintenance for a student with home fee status (this includes an EU student who has spent the previous three years (or more) in the UK undertaking undergraduate study).  Candidates with EU fee status are eligible for a fees-only award, but would have to provide funding for their living costs from another source such as personal funds or a scholarship.  The stipend will be £14,777 per year.  Information on fee status can be found at http://www.ox.ac.uk/admissions/graduate/fees-and-funding/fees-and-other-charges.

Any questions concerning the project can be addressed to Professor Simon Benjamin (simon.benjamin@materials.ox.ac.uk).  General enquiries on how to apply can be made by e‑mail to graduate.studies@materials.ox.ac.uk.  You must complete the standard Oxford University Application for Graduate Studies.  Further information and an electronic copy of the application form can be found at http://www.ox.ac.uk/admissions/postgraduate_courses/apply/index.html.

Also see homepages: Simon Benjamin

Circuit compilers for near-term quantum computers
Professor S C Benjamin

Intro: Quantum computers are presently reaching the scale where they can perform certain tasks more rapidly than any kind of conventional computer can. However, in order to maximize the potential of this first generation of quantum machines as they arrive, it is important to create quantum compilers – that is, methods to translate a task from a high level description (that, say, a human has designed) into the low-level operations (“gates”) that will occur inside the machine.

Summary: The number of elementary gates in a quantum computation determines the runtime of the quantum computer. It is clearly advantageous to have faster computations that use fewer gates and "circuit compilation" is the art of optimizing and automating this process.  For near-term quantum computers (without error correction) effective compilation is especially important because these devices will be noisy and this imposes a practical limit on the number of gates before an error becomes inevitable.  Therefore, compilation protocols and software are crucial to whether we will be able to demonstrate a quantum advantage before full blown error-corrected devices are available.  This PhD project will develop compilation methods exploring the following two directions. 

The project is a joint collaboration between the groups of Simon Benjamin in Oxford, and Earl Campbell in Sheffield. The project and student could be based at either university, according to the preference of the successful candidate. The studentship will be held at the chosen university and the student will be registered for a doctoral degree of the chosen university.

This NQIT hub EPSRC-funded 3.5-year PhD/DPhil studentship will provide full fees and maintenance for a student with home fee status (this includes an EU student who has spent the previous three years (or more) in the UK undertaking undergraduate study).  Candidates with EU fee status are eligible for a fees-only award, but would have to provide funding for their living costs from another source such as personal funds or a scholarship.  The stipend will be £14,777 per year.  Information on fee status can be found at http://www.ox.ac.uk/admissions/graduate/fees-and-funding/fees-and-other-charges.

Any questions concerning the project can be addressed to Professor Simon Benjamin (simon.benjamin@materials.ox.ac.uk).  General enquiries on how to apply can be made by e‑mail to graduate.studies@materials.ox.ac.uk.  You must complete the standard Oxford University Application for Graduate Studies.  Further information and an electronic copy of the application form can be found at http://www.ox.ac.uk/admissions/postgraduate_courses/apply/index.html.

Also see homepages: Simon Benjamin

Also see a full listing of New projects available within the Department of Materials.